When a USB device is repeatedly inserted and removed, the USB port may stop responding. This article describes how to resolve this problem with a unresponsive USB port.

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If you quickly and repeatedly insert and remove a USB device, the USB port may stop responding. When the port is in this state, it no longer recognizes any USB device.

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This problem may occur because of a race condition in the Selective Suspend feature of USB. Microsoft and the hardware vendors that manufacture the chips that are used for USB have investigated the problem. However, the results have been inconclusive because of the intermittent nature of the problem.

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To resolve this, follow these steps:

1.	Start Device Manager.
2.	On the Action menu, click Scan for New Hardware.

If this does not resolve the issue, you have to restart the computer. In some cases you must use Device Manager to disable then re-enable the device to get it to recover from this unresponsive condition.

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Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

To prevent this problem for server products where power management is not important or required, you can disable the selective suspend feature of USB. To do this, you must modify the following registry entry:Note If this registry key is not present, you must create it.

This setting affects all USB host controller drivers in the system. If the DisableSelectiveSuspend value is set to 1, the selective suspend feature is turned off and the Allow the computer to turn off this device to save power check box does not appear on the Power Management tab for the USB Root Hub.

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Microsoft is researching this problem and will post more information in this article when the information becomes available.

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